The present invention relates to methods for manufacturing electrical contact pins having a compliant part suitable for fitting into a plated-through-hole (PTH) of nor more than 0.93 mm (0.037") in diameter.
In general, electrical contact pins having a compliant part to be fitted into a relatively large PTH, for example 1.0 mm (0.040") in diameter, of a printed circuit board (PCB) for mechanical fixation and electrical connection thereto are well known. For examples, U.S. Pat. Nos. 4,186,982 and 4,513,499 disclose such conventional compliant electrical contact pins. These two examples will be briefly described below with reference to FIGS. 15-17.
The electrical contact pin of FIG. 15, so called "eye of the needle" compliant pin, is made by stamping from a sheet of springy conductive metal so that it has an opening 11 at the center of a compliant part 10 to give a spring property to the compliant part. As FIG. 16 shows this compliant part is fitted into a PTH 1 of a PCB so that its four corners 11A elastically penetrate the conductive wall of the PTH 1 for mechanical fixation and electrical connection thereto.
The electrical contact pin of FIG. 17 is made by first stamping out a compliant part 20 from a sheet of springy conductive metal. Then, the compliant part 20 is sheared to form a pair of legs 21 and 22. These legs are then offset with respect to each other along the shear plane so as to give a spring property to the compliant part. As FIG. 18 shows, the compliant part is fitted into a PTH 2 of a PCB so that a corner 21A of the offset leg 21 and a corner 22A of the offset leg 22 elastically penerate the conductive wall of the PTH 2 for mechanical fixation and electrical connection.
Recently, electronic parts are densely mounted on a circuit board, and the diameter of PTHs has become smaller than before. Consequently, there is a need to make the compliant part of an electrical contact pin smaller than before. However, it is practically impossible to punch out an opening 11 having a diameter of less than about 0.60 mm (0.024 inch) in the compliant part of an eye of the needle compliant pin of FIGS. 15 and 16. Although the compliant part of a contact pin of FIGS. 17 and 18 is relatively well fitted into a small PTH, there are only two points in contact with the conductive wall of the PTH as shown in FIG. 18, and the contact pin tends to turn during fitting operation. Consequently, the fitting operation requires an extra force to counter the turning force.